The present invention is directed to a computer control system for generating geometric designs in a tangible form. In one preferred embodiment, the invention is directed to a servo control system for machine tools which cut or form pieces of material, such as metal or wood, into desired geometric shapes.
Since the 1950's, servo control systems have been used for the control of machine tools, to automate repetitive machine operations. At first, these systems were large, complex, inflexible and expensive; operating in many ways like a player piano, with programs stored on paper tape. Over the years, these systems have evolved into powerful, reliable and reasonably priced fixtures of industry. Servo controls now integrated with computer technology are referred to as CNC or DNC systems (Computer Numerical Control or Direct Numerical Control). Along with production lines and the concept of interchangeable parts, machine tools equipped with CNC systems have become an integral part of modern mass production technology.
Even though CNC systems are highly economical for mass production of machined components, the vast majority of machine tools worldwide are still operated by hand. The reason for this apparent contradiction is that most machine tools are not used for mass production. Rather, they are used for prototyping, repair, or small quantity production.
If a machine is used to make large quantities of a single component, the time spent writing a CNC program and setting up the machine is quickly recovered during actual production. If the user is only interested in one sample of a part, however, he can typically make that one sample faster with manual control than he can program the CNC.
The obstacles to using prior CNC systems for small quantity production are the rigid demarcations between the stages leading to actual production on CNC machine tool systems. The desired part must first be designed, this design must then be translated into a "tool path" which will cut the part, and finally this tool path must be translated into codes (sometimes known as G-codes) for use by the CNC system. This three-step process is typically carried out by different people using different equipment in each step.
It is one objective of the present invention to provide automation techniques which allow small quantity production on machine tools and other equipment to be substantially improved, compared to either traditional manual or traditional CNC approaches. At present, about 95% of all machine tools are manual, so that more than 95% of machine operators are using manual machines (since one operator can sometimes service more than one CNC machine). A main objective of the present invention is to substantially improve the productivity of this large majority of operators. The direct value of such improved productivity will be very large and its "economic ripple effect" could be even larger.
There are several million manual machine tools in place worldwide. The techniques disclosed herein are applicable to the majority of these machines by means of adding or "retrofitting" computer control systems, which embody the principles of the present invention, to these machines. Although the present invention is directed primarily toward automation of existing and/or new manual equipment, the techniques disclosed herein will also benefit CNC machine tools used for mass production.
Part of the resistance to using CNC machines in the past for small quantity production is due to the large amount of processing power that is required. In conventional machine control environments, a large amount of processing power is required, and different parts of the manufacturing process are frequently carried out in different locations. Due to the distributed nature of tasks, computer aided drawing (CAD) or CAD/CAM (computer assisted manufacturing) operations are carried out on one processor and CNC operations are carried out with the use of several other processors. Typically, CNC systems have allocated one processor per motor being controlled, with each motor providing the driving force along one axis of machine operation. In addition, conventional CNC systems require another processor to coordinate the activities of these motor controllers, plus a processor to handle the user interface. No known multi-axis CNC system operates with a single central computational resource and without individual active axis controllers, which may be active analog feedback loops or digital feedback loops.
To enable manual machine tools to be automated in a manner which adapts them to be reliably and economically used for small quantity part production, two objectives are desireable. First, all of the tasks which were heretofore carried out in a distributed manner should be integrated into a single system that is controlled by one user through a consistent interface. Secondly, a control system should be available that provides coordinated control of movement along multiple axes in an economical manner with small processing power requirements.
The present invention is particularly directed to the latter of these two main objectives.